Phytohormones Regulate the Expression of Nuclear Genes Encoding the Components of the Plastid Transcription Apparatus

Abstract

As multifunctional regulators of physiological processes, phytohormones play an important role in the regulation of expression of the plastid genome and chloroplast biogenesis. Hormones can directly regulate the expression of genes localized in the chloroplast genome. However, many components of the plastid transcription apparatus are encoded by nuclear rather than plastid genes. It remains obscure whether these nuclear genes are subject to hormonal regulation. This is the first study to show that phytohormones exert differential effects on the expression of nuclear genes of the transcription machinery of the Arabidopsis thaliana plastome. RT-PCR analysis showed that the level of transcripts of the majority of studied genes was activated by trans-zeatin but decreased under the influence of ABA, methyl jasmonate, and salicylic acid, whereas ethylene had no significant effect, and the effects of brassinolide depended on the illumination conditions. The results of this study indicate that the hormonal regulation of the plastome expression can be mediated by differential regulation of the nuclear genes encoding plastid transcription machinery components.

Joint inhibition of mitochondrial complex IV and alternative oxidase by genetic or chemical means represses chloroplast transcription in Arabidopsis

“…In this context, a recent finding concerning the effects of phytohormones on the expression of nuclear genes of the plastid transcription machinery is noteworthy [42]. It was shown that ABA, MJ and SA decrease the expression of nuclear genes of the chloroplast transcription machinery, including sigma factors and PAPs [42], so their action results in a similar effect to that observed here for rps10 and aox1a: rpoTmp.…”

“…In this context, a recent finding concerning the effects of phytohormones on the expression of nuclear genes of the plastid transcription machinery is noteworthy [42]. It was shown that ABA, MJ and SA decrease the expression of nuclear genes of the chloroplast transcription machinery, including sigma factors and PAPs [42], so their action results in a similar effect to that observed here for rps10 and aox1a: rpoTmp. A significantly increased level of SA in rps10 leaf extracts (figure 8) supports the hypothesis that SA could act as a mediator in the signal transduction cascade from mitochondria to the nucleus to chloroplasts leading to a decline in the level of chloroplast transcription machinery components.…”

“…To gain insight into the signal transduction cascade leading to a decreased rate of chloroplast transcription, we looked for factors that down-regulate the expression of nuclear-encoded components of chloroplast transcription machinery, similarly to rps10 and aox1a:rpoTmp plants. Notably, a recent study showed that some of phytohormones, like abscisic acid (ABA), methyl jasmonate (MJ) and salicylic acid (SA), decrease the expression of nuclear genes encoding the components of plastid transcription apparatus [42]. Interestingly, one of the above-mentioned phytohormones, SA, was 1.5-to 2-fold increased in leaf extracts of both rps10 phenotypes compared with the wild-type (figure 8).…”

Arabidopsis Plastid-RNA Polymerase RPOTp Is Involved in Abiotic Stress Tolerance

“…The same authors obtained similar results in barley leaves [53]. In line with this, Danilova et al [54] found that most of the nuclear genes that encode different plastid transcriptional machinery components, including RPOTp and RPOTmp, were down-regulated in Arabidopsis seedlings exposed to ABA. This repressive effect of ABA on plastid gene expression could be mediated by alarmone guanosine-30-50-bisdiphosphate (ppGpp), which accumulates in chloroplasts in response to abiotic stress, and to ABA, jasmonate or ethylene hormones [55,56].…”

Nucleo‐plastidic PAP 8/ pTAC 6 couples chloroplast formation with photomorphogenesis

“…ESPRESSO transcripts cycle in a diurnal pattern and LIGHT1 responds to various wavelengths and has a significant epistatic interaction with LIGHT2/PHYB . A separate transcript analysis revealed that PAP8 responds to temperature (Danilova et al , 2018a) and phyto‐hormones (Danilova et al , 2018b). In the following, PAP8 will be used as the gene name for At1g21600 also corresponding to ESPRESSO , LIGHT1 or pTAC6 .…”